The present invention relates to a process for the preparation of homopolymers and copolymers of alpha monoolefins by means of a catalyst system comprising a titanium halide, an aluminum-alkyl, and a phenolic antioxidant compound which is included in the catalyst formulation to increase the activity of the catalyst and also its stereospecificity. Catalyst systems such as these are known in the art. One such catalyst system utilizing hindered phenolic compounds is disclosed in German Laid Open Application DAS No. 2,841,645. Other such compounds are disclosed in my copending, commonly assigned application entitled "Polyolefin Polymerization Catalysts Containing Sterically Unhindered Phenolic Compounds".
Under most operating conditions, it is possible to handle the above compounds in standard reactor feed systems and combine them together without encountering any special problems. It is normally advantageous to make a slurry or solution of the individual components or a combination thereof in heptane or some other inert solvent prior to combining them or introducing them into the polymerization reactor. The solubility of these compounds decreases as the temperature drops. Therefore, under conditions of low temperature, they have a tendency to crystallize out of the solution. If this were to occur in the reactor feed system, which is quite possible because it normally would be exposed to the elements, the detrimental effects would be incorrect stoichiometry of the components and possible plugging of feed lines, unless steam tracing is employed.
It is an object of this invention to provide an improved polymerization process whereby a catalyst system comprising a titanium halide, an aluminum alkyl, and a phenolic compound as described above can be used even under conditions of low temperature. It is a further object of this invention to provide a method to prevent the crystallization of such phenolic compounds in the reactor feed system under conditions of low temperature.